Spin valve structure with Si seed layer and reduced PtMn antiferromagnetic layer thickness

ABSTRACT

A magnetic head having a spin valve sensor that is fabricated utilizing an Al 2 O 3 , NiMn0, Si seed layer upon which a PtMn spin valve sensor layer structure is subsequently fabricated. In the preferred embodiment, the Si layer has a thickness of approximately 20 Å and the PtMn layer has a thickness of approximately 120 Å. An alternative fabrication process of the Si layer includes the overdeposition of the layer to a first thickness of from 15 Å to 45 Å followed by the etching back of the seed layer of approximately 5 Å to approximately 15 Å to its desired final thickness of approximately 20 Å. The Si layer results in an improved crystal structure to the subsequently fabricated PtMn and other spin valve sensor layers, such that the fabricated spin valve is thinner and exhibits increased ΔR/R and reduced coercivity.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to spin valve sensors formagnetic heads, and more particularly to an improved Si seed layer for aPtMn spin valve sensor structure.

2. Description of the Prior Art

Increasing the areal data storage density of hard disk drives can beaccomplished by reducing the written data track width, such that moretracks per inch (tpi) can be written on the disk, and/or by reducing thesize of data bits, such that the number of bits per inch (bpi) on a datatrack can be increased. However, to read data from a disk with anincreased bpi, it is also necessary to develop a sufficiently thin readgap within the read head of the magnetic head, such that unwantedmagnetic field interference from adjacent data bits is substantiallyeliminated. Current state of the art magnetic heads have read head gapsof approximately 800 Å to 1,000 Å.

Magnetic heads for hard disk drives typically have a read head portionincluding a magnetoresistive (MR) spin valve sensor structure forreading data from the disk of the hard disk drive. As is well known tothose skilled in the art, such MR sensor structures include a pluralityof thin film layers disposed between two magnetic shields that definethe read gap. The thin film layers have particular magnetic properties,and are sensitive to the magnetic field of the data bits on the harddisk. Thus, thinner layers disposed between the two magnetic shieldswill create a thinner read gap, which will allow the read head to detectthe smaller data bits that a higher bpi data track contains.Additionally, where one or more of the sensor layers can be madethinner, the electrical insulation layers (G1 and G2) within the sensorcan be made thicker, which reduces the incidence of electrical shortsthrough the G1 and G2 insulation layers.

The thin film layers of a typical MR spin valve sensor will include atleast one antiferromagnetic layer, at least one pinned magnetic fieldlayer, and at least one free magnetic field layer. When the magneticfield direction of the free magnetic field layer is parallel to themagnetic field direction of the pinned magnetic field layer, theelectrical resistance R of the MR sensor is lowest. When reading data, amagnetic data bit of a hard disk will cause the magnetic field directionof the free magnetic field layer to change, whereupon the electricalresistance of the sensor increases. This change in resistance (ΔR)affects the electrical current passing through the sensor, which is thusdetected as a data signal. The parameter ΔR/R is useful in comparingmagnetic head performance.

It is therefore desirable to develop MR sensors having a decreasedthickness, while maintaining or even increasing the ΔR/R value. Wherethe metallic MR sensor layers are made thinner, there is less shuntingof electrical current through these layers and away from the freemagnetic layer. This leads to an increase in ΔR and improved magnetichead performance. Another parameter that is significant in spin valvesensor performance is the free layer coercivity, and generally, thelower the coercivity, the more stable the MR sensor will be. Thus athinner sensor that maintains coercivity or even decreases coercivity isdesirable.

Many different materials have been utilized in the prior art in attemptsto increase ΔR/R and reduce the coercivity of the MR sensor. The presentinvention relates to a MR spin valve sensor that is fabricated utilizinga particular seed layer that replaces the prior art Ta sublayer with aSi sublayer. This allows the use of a thinner PtMn antiferromagneticlayer, thus leading to a thinner MR sensor, which allows for thicker G1and/or G2 insulation layers while maintaining the same read gapthickness.

SUMMARY OF THE INVENTION

The spin valve sensor of the present invention is fabricated utilizing athree part Al₂O₃, NiMnO, Si seed layer upon which a PtMnantiferromagnetic layer is subsequently fabricated. The prior art seedlayer is Al₂O₃, NiMnO, Ta. A preferred fabrication process of the seedlayer includes the sequential deposition of the three sublayer parts ofthe seed layer in a vacuum chamber.

In the preferred embodiment, the Si seed sublayer is formed with athickness in the range of from approximately 10 Å to approximately 40 Å,with a preferred thickness of approximately 20 Å, where the prior art Taseed sublayer is fabricated with a thickness of approximately 35 Å. Theuse of the Si sublayer also allows a reduction in the thickness of thePtMn antiferromagnetic layer that is fabricated thereon, from a priorart value of approximately 150 Å to approximately 120 Å in the presentinvention. Thus the thickness of the MR sensor layers is reduced byapproximately 15 Å in the seed sublayer, and by approximately 30 Å inthe PtMn antiferromagnetic layer, such that the thickness of the MRsensor is reduced by approximately 45 Å; that is, the insulationthickness can be increased by approximately 45 Å. This increasedinsulation thickness reduces the risk of electrical shorts from thesensor to the shields.

The present invention may also include the overdeposition of the Sisublayer beyond its desired thickness, followed by the etching back ofthe Si sublayer to its desired thickness. Thereafter, a thinner PtMnspin valve sensor layer is fabricated upon the Si sublayer. Regardingthe etched back Si sublayer embodiment, it is believed that the crystalstructure of the surface of the etched back Si sublayer is altered bythe etching process, and it results in an improved crystal structure tothe subsequently fabricated PtMn layer and other sensor layers, suchthat the fabricated sensor exhibits increased ΔR/R and reducedcoercivity.

In the etched back Si seed sublayer embodiment, the Si sublayer isdeposited to a first thickness of from 15 Å to 45 Å and is etched backfrom approximately 5 Å to approximately 25 Å. In a particularembodiment, the Si sublayer is deposited to an initial thickness ofapproximately 30 Å and is etched back a thickness of approximately 10 Åto achieve a final thickness of approximately 20 Å. The use of etchedback Si sublayer provides improved crystalline structure properties tothe PtMn antiferromagnetic layer as well as layers fabricated thereon,such that improved ΔR/R and coercivity properties of the magnetic headof the present invention are obtained.

It is an advantage of the magnetic head of the present invention that itincludes a magnetoresistive read head having a decreased sensorthickness.

It is another advantage of the magnetic head of the present inventionthat it includes a magnetoresistive sensor having a decreased sensorthickness, an increased ΔR/R and a reduced coercivity.

It is a further advantage of the magnetic head of the present inventionthat it includes a three part Al₂O₃, NiMnO, Si seed layer with a reducedthickness PtMn antiferromagnetic layer.

It is yet another advantage of the magnetic head of the presentinvention that it includes a magnetoresistive sensor including an Siseed sublayer portion having an improved upper surface crystallinestructure that results in a sensor having a reduced sensor thickness andan increased ΔR/R and a reduced coercivity.

It is an advantage of the hard disk drive of the present invention thatit includes a magnetic head of the present invention having amagnetoresistive spin valve sensor having a reduced sensor thickness.

It is another advantage of the hard disk drive of the present inventionthat it includes a magnetic head of the present invention that includesa magnetoresistive sensor having a reduced sensor thickness, anincreased ΔR/R and a reduced coercivity.

It is a further advantage of the hard disk drive of the presentinvention that it includes a magnetic head of the present invention thatincludes a three part Al₂O₃, NiMnO, Si seed layer, with a reducedthickness PtMn, antiferromagnetic layer.

It is yet another advantage of the hard disk drive of the presentinvention that it includes a magnetic head of the present invention thatit includes a magnetoresistive sensor including an Si seed layer portionhaving an improved upper surface crystalline structure that results in asensor having a reduced sensor thickness and an increased ΔR/R and areduced coercivity.

It is an advantage of the method for fabricating a magnetic head of thepresent invention that it includes a MR sensor structure including an Siseed layer portion, such that a reduced sensor thickness and anincreased ΔR/R and reduced coercivity results.

The foregoing and other objects, features, and advantages of the presentinvention will be apparent from the following detailed description ofthe preferred embodiments which make reference to the several figures ofthe drawing.

IN THE DRAWINGS

FIG. 1 is a top plan view generally depicting a hard disk drive thatincludes a magnetic head of the present invention;

FIG. 2 is a side cross-sectional view depicting a typical prior art spinvalve read head portion of a magnetic head;

FIG. 3 is a side cross-sectional view depicting typical thin film layersthat may be utilized in fabricating the prior art spin valve sensorstructure depicted in FIG. 2;

FIG. 4 is a side cross-sectional view depicting a first embodiment of aspin valve sensor structure of the present invention;

FIG. 5 is a side cross-sectional view depicting a second embodiment of aspin valve sensor structure of the present invention;

FIG. 6 is a graph comparing the performance characteristics of the Siseed sublayer magnetic head of the present invention with a prior art Taseed sublayer magnetic head; and

FIGS. 7, 8 and 9 are graphs providing performance data of the Si seedsublayer magnetic head of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a top plan view that depicts significant components of a harddisk drive which includes the magnetic head of the present invention.The hard disk drive 10 includes a magnetic media hard disk 12 that isrotatably mounted upon a motorized spindle 14. An actuator arm 16 ispivotally mounted within the hard disk drive 10 with a magnetic head 20of the present invention disposed upon a distal end 22 of the actuatorarm 16. A typical hard disk drive 10 may include a plurality of disks 12that are rotatably mounted upon the spindle 14 and a plurality ofactuator arms 16 having a magnetic head 20 mounted upon the distal end22 of the actuator arms. As is well known to those skilled in the art,when the hard disk drive 10 is operated, the hard disk 12 rotates uponthe spindle 14 and the magnetic head 20 acts as an air bearing sliderthat is adapted for flying above the surface of the rotating disk. Theslider includes a substrate base upon which the various layers andstructures that form the magnetic head are fabricated. Such heads arefabricated in large quantities upon a wafer substrate and subsequentlysliced into discrete magnetic heads 20.

A typical prior art magnetic head is fabricated to include a read headportion for reading data from the hard disk and a write head portion forwriting to a hard disk, and FIG. 2 is a generalized depiction of a priorart read head portion of a magnetic head which will serve as a startingpoint for the description of the novel read head features of the presentinvention that follow. As depicted in FIG. 2, the read head portion 30includes a first magnetic shield layer (S1) 34 that is fabricated uponthe surface 38 of a substrate base 42. A first insulation layer (G1) 44is fabricated upon the S1 shield 34 and a plurality of read head sensorlayers 50 are then fabricated upon the G1 layer 46. A detaileddescription of the sensor layers 50 is provided hereinbelow, and thenovel sensor layers of the present invention are then discussed. Usingphotolithographic and etching techniques, portions of the sensor layersare removed such that the central portions 50 depicted in FIG. 2 remain.Thereafter, hard bias elements 54 are fabricated next to the sensorlayers 50, electrical leads 60 are fabricated upon the hard biaselements 54, a second electrical insulation layer (G2) 64 is depositedacross the device followed by the fabrication of a second magneticshield (S2) 68, and a write head portion (generally indicated as 72) issubsequently fabricated to complete the magnetic head fabricationprocess.

The present invention is directed towards improvements in the specificlayers that comprise the sensor element 50 of the read head, and a moredetailed depiction of a typical prior art magnetoresistive (MR) spinvalve sensor, such as may be utilized as sensor 50 in the prior artmagnetic head of FIG. 2 is depicted in FIG. 3. As depicted in FIG. 3, aG1 electrical insulation layer 44 typically composed of Al₂O₃, isfabricated upon the S1 shield layer 34, that is typically composed ofNiFe. This is followed by a three part seed layer composed of an Al₂O₃sublayer 76, an NiMnO sublayer 80 and a Ta sublayer 84. Significantly,the composition of this type of three part seed layer is a focus of thepresent invention, as described in detail hereinbelow.

Following the seed layer deposition, a spin valve layer structure 90 isfabricated. As is seen in FIG. 3, the sequence of sensor layers in theprior art spin valve layer structure 90 is PtMn, CoFe, Ru, CoFe, Cu,CoFe, NiFe, Cu, Ta, and the typical thickness of the various layers isset forth in FIG. 3, and it is noteworthy that the prior art PtMn layeris particularly fabricated with a thickness of approximately 150 Å. Asis well known to those skilled in the art, the PtMn layer acts as anantiferromagnetic layer, the CoFe, Ru, CoFe layers act as a pinnedmagnetic layer, the Cu layer acts as a spacer layer, the CoFe, NiFelayers act as the free magnetic layer, the Cu layer acts as a spinfilter layer and the Ta layer acts as a cap layer.

Magnetoresistive spin valve sensors, such as are described herein,operate by detecting magnetic data bits written upon a hard disk througha change in electrical resistance within the spin valve sensor when thesensor is exposed to the magnetic field of the data bit. Specifically,the orientation of the free layer magnetic field is altered by themagnetic field of a data bit, and the change in the orientation of thefree layer magnetic field creates a change in the electrical resistanceof the sensor. The electrical resistance of the sensor is lowest whenthe free layer magnetic field is oriented parallel to the pinned layermagnetic field, and the resistance of the sensor increases when the freelayer magnetic field is oriented other than parallel to the pinned layermagnetic field direction. Thus, an improved sensor (such as the presentinvention) will have a greater change in resistance when exposed tomagnetic data bits, and this change in resistance is generallydesignated as ΔR, where R is the sensor resistance when the free layermagnetic field is parallel to the pinned layer magnetic field, and ΔR isthe change in resistance of the sensor when the free layer magneticfield is anti-parallel to the pinned layer magnetic field. The valueΔR/R basically is a representation of the percentage change in thesensor resistance, and it is utilized in comparing the qualities of spinvalve sensors.

Another significant performance parameter for comparing sensorperformance is the magnetic coercivity of the sensor, because thecoercivity is a measure of the stability of the sensor, and the lowerthe coercivity of the sensor, the more stable it is. Therefore, it is aperformance goal for the spin valve sensor of the present invention tohave a higher ΔR/R and lower coercivity. As will appear from thefollowing description the improved seed layer of the spin valve of thepresent invention results in the creation of spin valve sensors havingsuch a higher ΔR/R and a reduced coercivity.

FIG. 4 is a side cross-sectional view depicting a first spin valvesensor structure 92 of the present invention. The spin valve sensorstructure 92 includes a three part seed layer including an Al₂O₃sublayer 76, followed by an NiMnO sublayer 80, followed by an Sisublayer 94, and a spin valve layer structure is then fabricated on topof the three part seed layer. As with the prior art seed layer depictedin FIG. 3, the three part seed layer of the present invention depictedin FIG. 4 is fabricated in a vacuum system with multiple chambers wherethe three layers are sequentially deposited without exposure toatmosphere. A comparison of the spin valve sensor 92 of FIG. 4 with thatof FIG. 3 reveals the differences that the prior art 35 Å Ta seedsublayer portion 84 of FIG. 3 has been replaced with a 20 Å Si seedsublayer 94, and the PtMn layer thickness has been reduced fromapproximately 150 Å to approximately 120 Å. A comparison of theproperties of the spin valve sensors depicted in FIGS. 3 and 4 ispresented hereinbelow. A second preferred embodiment of the spin valvesensor of the present invention can now be described with the aid ofFIG. 5.

FIG. 5 is a side cross-sectional view depicting a second embodiment of aspin valve sensor 96 of the present invention. The spin valve sensor 96includes a three part seed layer, including an Al₂O₃ sublayer 76, anNiMnO sublayer 80 and an Si sublayer 98. A comparison of the spin valvesensor 96 of FIG. 5 with that of FIG. 4 reveals that the Si seedsublayer 98 of FIG. 5 has the same approximately 20 Å thickness as theSi seed sublayer 94 of FIG. 4. However, as is discussed herebelow, theperformance parameters of the spin valve sensor of FIG. 5 are improvedover those of the spin valve sensor of FIGS. 3 and 4. This performanceimprovement is due to a different fabrication process for the Si seedsublayer 98 of the spin valve sensor 96 depicted in FIG. 5.Specifically, whereas the Si seed sublayer 94 of the spin valve of FIG.4 was deposited to a thickness of 20 Å, the Si seed sublayer 98 of thespin valve sensor of FIG. 5 was deposited to a thickness ofapproximately 30 Å and then etched back approximately 10 Å to a finalthickness approximately of 20 Å. Thereafter, the 120 Å PtMn layer andsubsequent sensor layers, as shown in FIG. 4 are fabricated on top ofthe etched back Si seed sublayer 98 of FIG. 5. The three part seed layerof spin valve sensor 96 is preferably fabricated in a vacuum system withmultiple chambers, wherein the three parts 76, 80 and 98 of the seedlayer are sequentially deposited by utilizing three sequentialsputtering sources without exposure to atmosphere, followed by an ionbeam etching step to etch back the Si sublayer 98. It is therefore to beunderstood that the single fabrication difference between the spin valvesensors depicted in FIGS. 4 and 5 is that the 20 Åthick Si seed sublayer98 of FIG. 5 has been over deposited and subsequently etched back to a20 Å thickness, whereas the Si seed sublayer of the spin valve of FIG. 4was originally deposited to the 20 Å thickness. The etched back uppersurface 100 (shown as a roughened line) of the Si seed sublayer 98 hasan altered crystallographic surface, as compared to the deposited Sisublayer 94 of FIG. 4. It is believed by the inventor that the improvedproperties of the spin valve sensor depicted in FIG. 5 result from thealteration of the surface crystallography of the etched Si seed sublayer98 of FIG. 5, as compared to the deposited (without etch back) Si seedsublayer 94 of the spin valve sensor depicted in FIG. 4. The alteredcrystallography of the surface 100 then results in improvedcrystallography of the PtMn and further layers that are sequentiallydeposited on top of the surface 100.

For ease of comparison, the structures and performance characteristicsof the three spin valve sensors depicted in FIGS. 3, 4 and 5, arepresented in Table I. TABLE I Sensor Layers Ta 40 Å 40 Å 40 Å Cu 5 5 5NiFe 30 30 30 CoFe 15 15 15 Cu 20 20 20 CoFe 26 26 26 Ru 8 8 8 CoFe 1717 17 PtMn 150 120 120 Seed Layer Etch W & W/O — 10 Ta 35 — — Si — 20 20NiMnO 30 30 30 Al₂O₃ 30 30 30 PERFORMANCE ΔR/R (%) 8.6 8.4 8.8CHARACTERISTICS Hc 6.5 7.0 5.5 Hf −5 −3 −10

As can be seen in Table I, each of the spin valve sensors depicted inFIGS. 3, 4 and 5 is represented in a data column. The specificindication (W&W/O) regarding etching of the Ta seed layer of theembodiment depicted in FIG. 3 means that experimental data was developedfor devices wherein the Ta seed layer was etched and was not etched(that is, with and without surface etching). The experimental dataresults were that the performance characteristics were similar, meaningthat the performance of the Ta seed layer spin valve sensor 50 was notappreciably enhanced by etching the surface of the Ta seed layer.

In comparing the performance characteristics of the sensors depicted inFIGS. 3 and 4, it is seen that ΔR/R is slightly decreased, and thecoercivity Hc of the FIG. 4 disk is somewhat reduced. The reduction ofcoercivity is approximately 2 Oersted which can be of significance insome applications. Regarding the etched back Si seed layer sensor 96 ofFIG. 5, it has a ΔR/R showing an approximately 5% increase, and a H_(c)coercivity that shows a 1 Oersted decrease and an H_(f) coercivity thatshows a 5 Oersted decrease from the FIG. 3 sensor. Thus, it is seen thatthe spin valve sensor 92 of FIG. 4 provides some improvement over theprior art, while the sensor embodiment depicted in FIG. 5 possessesimproved performance characteristics due to the depositing andsubsequent etching back of its Si seed sublayer. Specifically, the 20 ÅSi seed sublayer 94 of the FIG. 4 sensor 92 lacks some of the improvedperformance characteristics of the etched back 20 Å Si seed sublayer 98of the sensor 96 depicted in FIG. 5.

With regard to preferred ranges for the deposited Si seed sublayerthickness and preferred ranges for etching back the Si seed sublayer, itappears that the improvements in performance characteristics of thepresent invention can be obtained where the Si seed sublayer 98 isinitially deposited from approximately 15 Å to approximately 45 Å, andthe etching back of the Si seed sublayer is conducted from approximately5 Å to approximately 15 Å. A final thickness range of the Si seedsublayer 98 is from approximately 10 Å to approximately 40 Å. Apreferred final thickness range of the Si seed sublayer 98 is fromapproximately 15 Å to approximately 35 Å, and a preferred finalthickness of the Si seed sublayer 98 is approximately 20 Å. Thus the Siseed sublayer 98 described in Table I was initially a 30 Å Si seed layerthat was etched back 10 Å to a final thickness of 20 Å.

As indicated above, the magnetic head of the present invention includesan Si seed sublayer having a reduced thickness together with a PtMnlayer having a reduced thickness, which together provide improvedperformance characteristics to the magnetic head. It is believed thatthe improved characteristics relate to an improvement in themicrostructure of the PtMn layer which forms an enhanced FCT crystalstructure phase during the magnetic head annealing process that isconducted to obtain the desired magnetic field direction and pinning asis known to those skilled in the art. FIG. 6 is a graphical depictioncomparing the exchange pinning field of magnetic heads as a function ofthe PtMn layer thickness. The graph compares the Hp pinning field of theSi seed sublayer head of the present invention with the prior art Taseed sublayer head, depicted in FIG. 3 and described hereabove. It canbe seen that the Si seed sublayer head of the present inventionmaintains a strong pinning magnetic field utilizing a decreasedthickness PtMn layer as compared with the prior art head.

FIGS. 7, 8 and 9 are graphical depictions of performance characteristicsof the Si seed sublayer magnetic head of the present invention. As canbe seen in FIG. 7, the sensor maintains its resistance R with the PtMnlayer thickness decreasing even below 110 Å. As depicted in FIG. 8, thevalue of ΔR maintains a relatively constant value where the PtMn layerthickness is decreased down to 110 Å. Likewise, as depicted in FIG. 9,the value ΔR/R of the magnetic head of the present invention retains afairly constant value where the thickness of the PtMn layer is decreaseddown to approximately 110 Å.

The Si seed layer 94 is expected to provide increased performanceresults for different types of spin valve layer structures, as are knownto those skilled in the art that include a PtMn antiferromagnetic layer,such as a dual antiparallel pinned layer spin valve, in which two PtMnlayers are used.

While the present invention has been shown and described with regard tocertain preferred embodiments, it is to be understood that those skilledin the art will no doubt develop certain alterations and modificationsin form and detail therein. It is therefore intended that the followingclaims cover all such alterations and modifications that neverthelessinclude the true spirit and scope of the present invention.

1. A method for fabricating a magnetic head including a spin valvesensor, comprising the steps of: fabricating a first electricalinsulation layer (G1) above a first magnetic shield layer (S1);fabricating a plurality of spin valve sensor layers above said G1 layer,said spin valve sensor layers including a seed layer, a PtMnantiferromagnetic layer, at least one pinned magnetic layer and at leastone free magnetic layer; wherein said seed layer includes seed sublayersincluding Al₂O₃, NiMnO and Si.
 2. A method for fabricating a magnetichead as described in claim 29 wherein said Si seed sublayer isfabricated to have a thickness of approximately 10 to 40 Å.
 3. A methodfor fabricating a magnetic head as described in claim 29 wherein said Siseed sublayer is fabricated to have a thickness of approximately 20 Å.4. A method for fabricating a magnetic head as described in claim 30wherein said PtMn layer has a thickness of approximately 120 Å.
 5. Amethod for fabricating a magnetic head as described in claim 29 whereinsaid Si seed sublayer is fabricated to have a thickness of approximately20 Å and said PtMn layer has a thickness of approximately 120 Å.
 6. Amethod for fabricating a magnetic head as described in claim 33 whereinsaid spin valve sensor layers include at least one pinned magnetic layerhaving a composition including CoFe and at least one spacer layer havinga composition including Cu, and at least one free magnetic layer havinga composition including Co or CoFe.
 7. A method for fabricating amagnetic head as described in claim 29 including the further step ofetching a surface of said Si sublayer prior to the deposition of saidPtMn layer thereon.
 8. A method for fabricating a magnetic headincluding a spin valve sensor, comprising the steps of: fabricating afirst electrical insulation layer (G1) above a first magnetic shieldlayer (S1); fabricating a plurality of spin valve sensor layers abovesaid G1 layer, said spin valve sensor layers including a seed layer, aPtMn antiferromagnetic layer, at least one pinned magnetic layer and atleast one free magnetic layer; wherein said seed layer is comprised ofAl₂O₃, NiMnO, Si sublayers, and wherein said Si sublayer is fabricatedby depositing it to a first thickness and subsequently etching it backto a final thickness before the fabrication of said PtMn layer.
 9. Amethod for fabricating a magnetic head as described in claim 36 whereinsaid Si sublayer is fabricated to have a final thickness of fromapproximately 10 Å to approximately 40 Å.
 10. A method for fabricating amagnetic head as described in claim 37 wherein said Si sublayer isfabricated to have a final thickness of approximately 20 Å.
 11. A methodfor fabricating a magnetic head as described in claim 37 wherein said Siseed sublayer is fabricated to have a thickness of approximately 20 Åand said PtMn layer has a thickness of approximately 120 Å.
 12. A methodfor fabricating a magnetic head as described in claim 39 wherein saidspin valve sensor layers include at least one pinned magnetic layerhaving a composition including CoFe and at least one spacer layer havinga composition including Cu, and at least one free magnetic layer havinga composition including Co or CoFe.